1. Field of the Invention
The present invention relates generally to a relative displacement device with both slight push force and strong elastic pull force. The relative displacement device includes two displacement members, which can be displaced relative to each other. At a push stage of the displacement travel, the displacement member can be pushed with slighter push force. At an elastic pull stage of the displacement travel, the displacement member is elastically pulled by stronger elastic pull force. Accordingly, the relative displacement device of the present invention is applicable to large-size portable electronic products.
2. Description of the Related Art
Following the advanced development of electronic industries, portable electronic products make progress in pattern and function every day. Especially, for convenience in operation, the designs of human-machine interfaces of various electronic products, such as mobile communication devices (mobile phones), laptops, handheld game machines and personal digital assistants (PDA), have been more and more emphasized. In order to increase the range for the interface without enlarging the total area or volume of the product, various fold structures (snap-on covers) and slide structures (slide covers) have been developed. Although the fold products were developed earlier, the slide products are better than the fold products in appearance, function and operational convenience. As a result, the slide products have nearly totally substituted for the fold products and become most popular pattern nowadays.
At an early stage, the slide cover almost thoroughly needs to be pushed by an operator's hand and has poor hand touch feeling in operation. Therefore, the conventional slide cover needs to be improved in operational convenience. A later improved model has an end-stage automatic slide design. Accordingly, after an operator pushes the cover from a start point to a position close to an end point of the travel, the device itself will apply a resilient force to the cover for pushing the cover to the end point. This preliminarily improves the shortcoming existing in the conventional slide cover.
FIGS. 1 to 4 show a typical structure of the above slide design. The slide cover device includes an upper cover 11, a substrate 12, a torque spring 13, an arcuate restriction plate 14 and a tension spring 15. The upper cover 11 has slide rails 113 for mounting the upper cover 11 on the substrate 12. In addition, the upper cover 11 is formed with an elongated slot 111 and a stepped slot 112 in communication with the slot 111. A first end of the tension spring 15 is affixed to a head end of the slot 111, while a second end of the tension spring 15 is affixed to a slider 16 disposed in the stepped slot 112. A first end of the arcuate restriction plate 14 is connected with the slider 16. A first end of the torque spring 13 is affixed to a fixing block 17.
A fixing hole 121 is formed on a first side of the substrate 12 in which a second end of the torque spring 13 is fixed. Two slide channels 122 are formed on the first side and a second side of the substrate 12 in which the slide rails 113 are inlaid respectively. A second end of the arcuate restriction plate 14 is affixed to the second side of the substrate 12 opposite to the fixing hole 121, whereby the arcuate restriction plate 14 can swing with the sliding movement of the upper cover 11.
When the upper cover 11 is moved downward by a travel, the arcuate restriction plate 14 is swung downward (as shown by phantom line of FIG. 3) and the slider 16 is moved rightward. At this time, the tension spring 15 is extended to exert a pull force onto the slider 16. Also, the torque spring 13 is deformed into a compressed state (as shown by phantom line of FIG. 3) to store elastic energy. Under the elastic force of the torque spring 13, the upper cover 11 is kept positioned on an upper side. However, when the fixing block 17 of the upper cover 11 passes over a horizontal reference axis of the fixing hole 121, the torque spring 13 is moved downward to release the elastic energy and restore to its home state (as shown by phantom line of FIG. 4). Simultaneously, the upper cover 11 is driven to move downward and the arcuate restriction plate 14 is swung downward. At the same time, the tension spring 15 contracts to keep the upper cover 11 located at a lower end as shown in FIG. 4.
FIGS. 5 to 8 show another type of conventional slide cover structure. The slide cover structure includes a substrate 22, an upper cover 21 disposed on one face of the substrate 22, two springs 23 arranged between the upper cover 21 and the substrate 22 and two plastic washers 24 on which the springs 23 are fitted. The washers 24 serve to reduce friction between the springs 23, the upper cover 21 and the substrate 22 and avoid damage thereof. First ends of the springs 23 are rotatably disposed in two holes 221 formed on two sides of the substrate 22 respectively. Second ends of the springs 23 are rotatably fitted on two fixing blocks 17 of the upper cover 21.
When the upper cover 21 is moved downward, the left spring 23 is moved downward as shown in FIG. 7, whereby the right and left springs 23 are both deformed into a compressed state to store elastic energy. According to the positional relationship between the fixing blocks 17 and the holes 221 of the substrate 22, it is known that the upper cover 21 is still positioned in a buffering area. At this time, under the elastic force of the springs 23, the upper cover 21 is kept positioned on an upper side. However, when the fixing blocks 17 of the upper cover 21 pass over a horizontal reference axis of the fixing holes 221 (as shown in FIG. 8), the right spring 23 is driven by the upper cover 21 to move downward and release the elastic energy. At this time, the right and left springs 23 both restore to their home states (as shown by phantom line of FIG. 8). Under such circumstance, the upper cover 21 is located at a lower end.
FIGS. 9 to 12 show a locating device of a large-size slide cover for reinforcing the elastic structure thereof. The locating device includes an upper cover 31 having longitudinal slide channel rails 34 and a transverse slot 312, and two elastic members 33 each having a fixed end 332 and a free end. The fixed ends 332 of the elastic members 33 are affixed to two ends of the slot 312, while the free ends of the elastic members 33 are connected with two sliders 333. The sliders 333 are slidably inlaid in the slot 312 and directed to the middle of the slot 312. The upper cover 31 is formed with a substantially U-shaped configuration and has two folding edges 310 extending from two sides of the upper cover 31 to form two channels for mounting the slide channel rails 34 therein. Two ends of the slot 312 are formed with holes for fixedly receiving the fixed ends 332 of the elastic members 33 therein.
Two slide rails 321 are formed on two sides of the substrate 32 for slidably inserting the slide channel rails 34 therein. Each slide channel rail 34 is formed with a channel in which the slide rail 321 is inlaid. The slide channel rail 34 further has two stopper plates disposed at two ends of the slide channel rail 34 for fixing the slide channel rail 34 in the channel of the upper cover 31. Two boomerang-shaped guide slots 322 are formed on the substrate 32 opposite to each other. The sliders 333 are also slidably inlaid in the guide slots 322. The middle sections of the guide slots 322 have two pass points 334, 335 at the peaks of the guide slots 322 opposite to each other. The pass points 334, 335 define a buffering area X. After the sliders 333 move in a certain push direction to at least pass over the pass points 334, 335 of the buffering area X, the upper cover 31 will automatically continuously move in the push direction to complete the slide-out or slide-in travel.
FIGS. 13 to 16 show a large-size half-automatic slide cover structure adapted to a notebook or a laptop. The slide cover is installed on a back face of main body of the notebook and can be slid out or slid in relative to the main body.
The slide cover structure includes a fixed member 41 fixed on a back face of a first display screen. The fixed member 41 has a mount body on which at least one fixed roller unit 412 and at least one movable roller unit 414 are mounted. The movable roller unit 414 is arranged on a movable board 415 connected to an elastic member 416 for providing elastic force.
The slide cover structure further includes a slide board 42 fixed on the slide cover. The slide board 42 has at least one straight rail 421 and at least one boomerang-shaped rail 422, 423 unparallel to the straight rail 421. The fixed roller unit 412 is restrictedly movable along the straight rail 421, whereby the slide board 42 can linearly move along the straight rail 421 relative to the fixed member 41 to drive the slide cover. The movable roller unit 414 is movable along the boomerang-shaped rails 422, 423 and displaceable in a direction normal to the straight rail 421 to deform the elastic member 416. Accordingly, the elastic member 416 serves to automatically slide out or slide in the slide board 42.
It can be found from observing the above conventional relative displacement units that the elastic members are all symmetrically arranged. That is, at the anterior stage of the slide-out or slide-in travel, the elastic force gradually increases with the displacement until the displacement member reaches the middle turning point. After the displacement member passes over the middle turning point, the elastic members will release the elastic energy to half-automatically push the displacement member to the end point of the travel and locate the displacement member at the end point. Such structure fails to allow a weaker push force at the anterior stage of the travel and provides a stronger half-automatic elastic pull force at the posterior stage of the travel. In the case that the conventional structure is applied to a small-size product such as mobile phone, handheld game machine or PDA, the slide cover can be easily operated. However, in the case that such structure is applied to a large-size product such as a notebook or a more and more popular tablet PC (as shown in FIGS. 9 to 16), the relative displacement member will have heavier weight adapted to the volume of the large-size product. Under such circumstance, it is necessary to increase the automatic elastic pull force at the posterior stage of the travel for fully elastically pulling the displacement member to its true position. Accordingly, the elastic coefficient of the elastic member must be increased in adaptation to the large-size displacement member. As a result, the manufacturing cost is increased and the push force at the anterior stage of the travel is also inevitably increased. This causes heavier burden to the user in operation. Moreover, at the end of the travel, in case of excessively large elastic pull force, the product may be damaged and the lifetime of the product may be shortened.